Method and apparatus for stiffening fabric edges



Dec. 18, 1951 E. s. KENNEDY 2,578,889

METHOD AND APPARATUS FOR STIFFENING FABRIC EDGES Original Filed June 28,1944 2 SHEETS-SHEET 1 RA 0/0 FREQUENCY 056/1 L A T05 mzqunvcv 5 i 2OSCILLATDR 23 Q Q RAD/o F If 032551;: 229'- 1 =0 #14 0/0 FPEQUEWC YOSCILLA 70R D F2: 2 BY JINVENTOR.

ATTORNEY E. S. KENNEDY Dec. 18, 1951 2 SHEETS-SHEET 2 Original FiledJune 28, 1944 IN VEN TOR.

ATTORNEY mE 3G8 h ..m N y 11 m a Q m. 2 Q /u n 1 Q 3 h d wV w* m :55 J 9o 0 s a A 3 F v 2 I M m 3 8 0 RN Patented Dec. 18, 1951 METHOD ANDAPPARATUS FOR STIFFENING FABRIC EDGES Edgar S. Kennedy, Wayne, Pa.,assignor to American Viscose Corporation, Wilmington, DeL, a corporationof Delaware Original application June 28, 1944, Serial No.

542,459. Divided and this application December 9, 1947, Serial No.790,592

11 Claims.

This invention relates to knitted fabrics comprising thermoplasticfibers, and to methods and apparatus for the production thereof, and itis the primary object of this invention to produce knitted fabrics whoseselvages are substantially free of curl and have little or no tendencyto develop a curled condition during the ordinary process of finishing.This application is a division of my copending application Serial No.542,459, filed June 28, 1944, now Patent No. 2,448,032.

While the invention is applicable generally to flat knitted fabricsWhose edges have a tendency to curl because of liveliness of twist, thatis, any

plain knit fabric, it is of special advantage as applied to warp knitfabrics, and its application will be described with reference to themanufacture of a tricot or warp knit fabric. Such curling of the edgescauses great difficulty in stitching the edges together to form a tubepreparatory to dyeing and finishing processes. If dyeing and finishingis to be performed by passing the fabric through a tenter frame, eitherclip or pin, there is difficulty in properly feeding the fabric to thetenter or the curled edge portions thereof must be Wasted. In eithersystem, it has been customary to cut the curled selvage from the fabricas waste at the stage of garment cutting. As this curled edge frequentlyamounts to a width of as much as an inch or two and sometimes more, itcan be seen that such waste has been substantial.

Generally, my invention involves the application of a substantially dryinternal heat by means of a high frequency electric field to the fabricedges as it proceeds from the knitting needles to a take-up roller ormandrel. At this time, the fabric is under tension and by applying heatclose to the needles there is little opportunity for it to manifest itstendency to curl and it is travelling slowly so that precise control ofthe heating effect upon the fabric edges can be readily exercised. Byapplying dry internal heat, there is substantially no tendency for thedisposition of the fibers in the individual yarns of the fabric tobecome altered by surface tension, or adhesive efiects exerted by thepresence of moisture alone or in conjunction with sizing materialcarried by or within the yarns. In addition, the thermoplastic fibersexposed on the surface of the yarns do not sufier any seriousdeformation and loss of fiber identity while those within are brought tosuflicient temperature to relieve internal fiber stresses and to becomeadhesive to bind fibers in the yarns. In this manner, a uniformactivation of the thermoplastic fibers is obtained throughz out thefabric, and the setting of the fabric edges to control curling isobtained without undue loss of pliability, softness, porosity, handleand the like.

The knit fabrics may consist entirely of heatactivatable fibers or maycomprise them in any desired substantial proportion together withnonactivatable fibers. By "heat-activatable" is meant those fibers whichare capable of being rendered adhesive upon the application of heat. Bynonactivatable or non-adhesive fibers is meant any which are notrendered adhesive by the treatment used in activating theheat-activatable fibers.

The potentially adhesive fibers may be composed of a wide variety ofmaterials, and may comprise any material capable of being formed intofibers which have an inherent tackiness upon heating to temperaturesbelow that at which the non-activatable fibers are damaged or renderedtacky and which are non-tacky at room temperature. Examples of theheat-activatable fibers include such thermoplastic fibers or filamentsas those of cellulose acetate or other cellulose esters and others ormixed esters, such as cellulose acetate propionate or cellulose acetatebutyrate, preferably in plasticized condition; also, resins, eitherpermanently thermoplastic or thermosetting but in the thermoplasticstate, formed by the polymerization or condensation of various organiccompounds such as coumarone, indene or related hydrocarbons, vinylcompounds, styrene, sterols, phenol-aldehyde resins either unmodified ormodified with oils, urea-aldehyde resins, sulfonamide-aldehyde resins,polyhydric alcoholpolybasic acid resins, drying oi] modified alkydresins, resins formed from acrylic acid, its homologues and theirderivatives, sulfur-olefine resins, resins formed from dicarboxylicacids and diamines (nylon type) synthetic rubbers and rubbersubstitutes, herein called resins," such for example as polymerizedbutadiene, olefine polysulfides, isobutylene polymers, chloroprenepolymers; and fibers formed from a resin comprising the product ofcopolymerizing two or more resins, such as copolymers of vinyl halideand vinyl acetate. copolymers of vinyl halide and an acrylic acidderivative; and also a mixture of resins, such as a mixture of vinylresins and acrylic acid resins or methacrylic acid resins, a mixture ofpolyolefine resins and phenol-aldehyde resins, or a mixture of two ormore resins from the different classes just named. There may be employedalso fibers made from rubber latex, crepe rubber, gutta percha, balata,and the like.

Further, the potentially adhesive fibers may be mixtures of thecellulose derivatives with resins or rubber, such as, a mixture ofcellulose nitrate and an acrylic acid resin, or a mixture of benzylcellulose and a vinyl resin, or a mixture of ethyl cellulose andshellac.

A preferred class of vinyl resins from which the fibers may be formedare the eopolymers of vinyl chloride with vinyl acetate or vinyl cyanideand after-chlorinated copolymers of vinyl chloride and vinyl acetate.

The resins above mentioned may be classified (a) Heat non-convertibleresins such for example as glycol polybasic acid resins, vinyl resins(particularly those of the preferred class above) iifid the acid typephenolaldehyde resins and the (b) Heat-convertible or thermosettingresins H such for example as glycerol-polybasic acid resins, polyolefineresins, phenol-aldehyde resins and the like.

(0) An element-convertible resin (which becomes infusible through theaction of certain elements, such as oxygen and sulfur) such for exampleas glycerol-polybasic acid-drying oils resins and olefine-sulfur resins.

Among the non-adhesive fibers which may be used are wood-pulp fibers,cotton, fiax, jute, kapok, silk, and the like, or synthetic fibers orfilaments of cellulosic composition, such as a cellulose or regeneratedcellulose, cellulose derivatives, such as cellulose esters, mixedcellulose esters, cellulose ethers, mixed cellulose esterethers, mixedcellulose ethers, cellulose hydroxyethers, cellulose carboxy-ethers,cellulose etherxanthates, cellulose xanthofatty acids, cellulosethiourethanes; natural and synthetic rubber and derivatives thereof whenthe potentially adhesive fibers become tacky at a sufiiciently lowertemperature than the rubber or derivative thereof alginic acid,gelatine, casein; mineral fibers or filaments such as spun glass,asbestos, mineral wool and the like; fibers or filaments made of naturaland synthetic resins which should be of such type that they are notrendered tacky when the potentially adhesive fibers are rendered tackyby heating; and the fibers made by slitting, cutting or shreddingnon-fibrous films, such as waste cellophane.

Prior to the knitting or even as they are fed to the needles of theknitting machine, the yarns may be treated with sizings or they may bemoistened. They may carry a sizing or a lubricant, or some otherconditioning agent applied at some earlier stage of fabrication, and thesized yarns may be moistened as they proceed to the knitting needles.Again the selvages of the fabric may be moistened very shortly afterleaving its line of formation at the knitting needles but prior toentering the heating device. Such moistening may be effected by wateralone, or when the yarns are of extremely low conductivity because of anunsized condition, those from which the fabric edges are formed may bemoistened by a dilute electrolyte, such as a dilute salt solution toincrease the conductivity of the edge portions. This may advantageouslybe applied in the case of hydrophobic vinyl resin yarns. However, manymaterials, such as cellulose acetate, from which the yarns may be formedare sufficiently hygroscopic so that their moisture content when inequilibrium with the normal conditions of temperature and humidityrenders them sufficiently conductive without additional moistening fortreatment in accordance with the present invention. Accordingly,cellulose acetate yarns carrying merely a lubricant, such as ethyleneoxide condensation product of sorbitan oleates, may be knit in the drycondition, and have their selvages treated to prevent curling. Inaddition, the activatable fibers themselves may be so producedartificially in the first instance as to be constituted of or contain aheat-conductive material. Thus a material such as graphite or metallicpowders may be distributed in this manner more or less homogeneouslythroughout the fiber or filament mass, or it may be localized in thecore of the fiber or filament or upon the surface thereof.

Any suitable high frequency oscillator may be employed for the purposeof the invention and the voltage at which it is operated may be variedwidely within the limits determined by the development of a coronadischarge between the electrodes. A frequency of from ten to thirtymegacycles per second is entirely satisfactory,-

the particular frequency employed in any par ticular case pending uponthe allowable voltage and the amount of power desired.

Pressure may be applied to the fabric edge while it is being subjectedto the high frequency electric field and such pressure mayadvantageously be applied through the medium of the electrodesthemselves, such electrodes being insulated in such case. While theapplication of pressure is by no means necessary, it generally serves tomore reliably and effectively control the extent of adherence betweenthe adhesive and non-adhesive filaments in the product.

The operating characteristics of the oscillator system including power,voltage, relationship of fabric speed to electrode area, conductivity ofyarns and pressure of electrodes are so correlated as to produce thedesired heating effect which depends upon the particular thermoplasticmaterial in the fabric. Thus, a temperature of 250 F. is effective upona cellulose acetate fabric in equilibrium with the atmosphere while atemperature of F. is effective for Vinyon.

An illustrative arrangement is shown in the drawing in which Figure 1 isa diagrammatic side elevation of one embodiment of the invention inassociation with a warp knitting machine;

Figure 2 is a top view of this embodiment at right angles to Figure 1;

Figure 3 is a modification looking in the longitudinal direction of thefabric;

Figure 4 is a view of another modification looking in the direction ofthe fabric; and

Figure 5 is a view illustrating the application of the invention to afull-fashioned hosiery machine.

With reference first to Figures 1 and 2, a plurality oi the yarns 2 and3 supplied by warp beams (not shown) are shown proceeding to guides 4and 5, then to the needles 6 and sinkers 1 associated operatively withthe presser bar 8 to perform the knitting cycle repeatedly to form thefabric 9 which then passes under tension beneath a roll in to the clothtake-up beam H driven in conventional fashion. Along each edge of thefabric, there are disposed upper and lower electrodes l2 and [3respectively which are connected to opposite terminals of a highfrequency oscillator by means of the leads l4 and I5.

The lower electrodes are stationary and while the upper electrodes mayalso be fixed, it is preferable that they be resiliently pressed againstthe fabric, such as by springs l5.

was

1m 3.1a modifiedmrrangcment of elecshown in which the fabric. passes:between-opposed. electrodes 2 I: which may or may ot beDressedlazainstwthe fabric, butare at least i in; close proximitythereto. A. third electrode!!! (Whiflhl may or may not bearcuate asshown) is arranged adjacent the edge of the fabric and is connectedto apole of. the oscillator opposite. to that towhich both the otherelsetrodes. are connected. If desired, one or the other-of theelectrodes It may be omitted. Electrodeii is spaced so that its centerline runs approximatclylalong the inner limit of the portiorrof the edgewhich ordinarily curls up.

In Figure 4 a lower electrode23 :isspaced inwarfllyfrom the edge of thefabric and an upper electrodeMlconnectcd-to an opposite pole of theoscillator 25;. This arrangement in which the electrodes are offset fromeach other on opposite sides of the fabric, setsu-p eddy currents acrossthawidth of. the. fabric extending between the two; electrodes and is a,preferredarrangement.

In Figure 5, there is shown a flat knitting machlneunit, such as.in usefor the production of full-fashioned hosiery comprising the supportingframe 26 and the narrowing frame arms 21 which is rocked in conventionalfashion in response to a conventional narrowingcam and associatedlinkage. andcarriesthebars. 2B and 29 which in turn carry the fingers 30and 3i and are moved longitudinally to narrow or widen the fabric. byconventional controlling mechanism. As the. fabric proceeds from theneedles 32 to the take-up 33, its selvage regions pass betweencorresponding pairs of electrodes. 34 and 35 connected-to opposite poles36 and 31 of a radio frequency oscillator 38. Each pair of electrodes iscarried by an arm 39 which is slidably mounted on a guide 40 secured tothe frame 26. As shown, the arm 39 and guide 40 have a dovetail shapedconnection. Arm 39 has an upwardly extending branch provided with anarcuate slot 4| through which a pin 42 secured to a lateral projection43 on the bar 29 extends. A washer 44 held in place on pin 42 by acotter pin 45 provides a positive connection for imparting thelongitudinal movement of the narrowing bar 29 to the arm 39 carrying theelectrodes while the arcuate slot permits the rocking movement of thebar 43. A similar connection (Ma and 42a) is provided between the pairof electrodes at the other side of the fabric and the narrowing bar 28.In this manner, a constant width strip of fabric adjacent each salvageis treated to prevent curling regardless of the position of the selvagesduring knitting when narrowing or widening occur. The upper electrodes35 may be pivotally mounted as at 46 to permit them to be swung out ofthe way during the operation of turning the welt.

The description herein is intended to be illustrative only and it is tobe understood that changes and variations may be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

I claim:

1. A method comprising the steps of fiat-knitting a fabric from yarnscomprising thermoplastic fibers carrying a conditioning agent,moistening a narrow portion along each of the selvages with an aqueousmedium, passing the fabric under tension from the line of its formationto a take-up position, and subjecting only the portions along theselvages during such passage under tension to a high frequency electriccurrent to render thermoplastic fibers therein tacky and thereby tobind'fibers-in the-fabric and simultaneously to dry the salvageportions.

2. In combination, a machine for flat-knitting a fabric having a row ofknitting needles anda fabric take-up roll, means for tensioning thefabric as it passes from the needles to the takeup roll andmeansadjacent the selvages comprising a pair of electrodes on opposite sidesof the fabric for subjecting a narrow portion along each of the selvagesto a high frequency electric current, the electrodes of each pair beingoffset laterally in the direction of the fabric width.

3. In combination, a machine for fiat-knitting a fabric having a row ofknitting needles, a fabric take-up roll, and narrowing and wideningmechanism, means for tensioning the fabric as it passes from the needlesto the take-up roll, means adjacent the selvages comprising electrodesalong opposite edges of the fabric for subjecting a. nar-- row portionalong each of the selvages to a high frequency electric current, andmeans for moving the electrodes transversely of the fabric in responseto the motion of the narrowing and widening mechanism.

4. In combination, a machine for fiat-knitting a fabric having a row ofknitting needles, a fabric take-up roll, and a narrowing and wideningmechanism, means for tensioning the fabric as it passes from the needlesto the take-up roll, means adjacent the selvages in front of the needlescomprising a. pair of electrodes on opposite sides or the fabric forsubjecting a narrow portion along each of the selvages to a highfrequency electric current, means for moving the electrodes in responseto the movement of the narrowing and-widening mechanism, the upperelectrodes being pivotally mounted to permit swinging thereof laterallyof the fabric.

5. In combination, a machine for fiat-knitting a fabric having a row ofknitting needles, a fabric take-up roll, and a narrowing and wideningmechanism comprising narrowing bars, means for tensioning the fabric asit passes from the needles to the take-up roll, means adjacent theselvages in front of the needles comprising a pair of electrodes forsubjecting a narrow portion along each of the selvages to a highfrequency electric current, each part of electrodes being connected tothe narrowing bar controlling the corresponding selvage of the fabric.

6. The method of preventing curling of the edges of a textile fabriccomprising thermoplastic fibers and having a tendency to curl at theedges comprising internally heating a narrow portion only thereof alongeach of the selvages thereof by the application of a high frequencyelectric current to raise the temperature of the fibers inside the yarnsto a temperature which relieves internal fiber stresses and renders thefibers adhesive to bind the fibers in the interior of the yarns withoutserious deformation or loss of fiber identity in the fibers exposed onthe surface of the yarns.

7. The method of preventing curling of the edges of a flat knit fabriccomprising thermoplastic fibers comprising internally heating a narrowportion only thereof along each of the selvages thereof by theapplication of a high frequency electric current to raise thetemperature of the fibers inside the yarns to a temperature whichrelieves internal fiber stresses and renders the fibers adhesive to bindthe fibers in the interior of the yarns without serious deformation orloss of fiber identity in the fibers exposed on the surface of theyarns.

8. A method comprising the steps of flat-knitting a fabric from yarnscomprising thermoplastic fibers, passing the fabric under tension fromthe line of its formation to a take-up position, and internally heatinga narrow portion only thereof along each of the selvages during suchpassage under tension by the application of a. high frequency electriccurrent to raise the temperature of the fibers inside the yarns to atemperature which relieves internal fiber stresses and renders thefibers adhesive to bind the fibers in the interior of the yarns withoutserious deformation or loss of fiber identity in the fibers exposed onthe surface of the yarns.

9. A method comprising the steps of fiat-knitting a fabric from yarnscomprising cellulose acetate while in normally dry condition, passingthe fabric under tension from the line of its formation to a take-upposition, and internally heating a narrow portion only thereof alongeach of the selvages during such passage under tension by theapplication of a high frequency electric current to raise thetemperature of the fibers inside the yarns to a temperature whichrelieves internal fiber stresses and renders the fibers adhesive to bindthe fibers in the interior of the yarns without serious deformation orloss of fiber identity in the fibers exposed on the surface of theyarns.

10. A method comprising the steps of flatknitting a fabric from yarnscomprising thermoplastic fibers carrying a conditioning agent, passingthe fabric under tension from the line of its formation to a take-upposition, and internally heating a narrow portion only thereof 3 alongeach of the selvages during such passage under tension by theapplication of a high frequency electric current to raise thetemperature of the fibers inside the yarns to a temperature whichrelieves internal fiber stresses and renders the fibers adhesive to bindthe fibers in the interior of the yarns without serious deformation orloss of fiber identity in the fibers exposed on the surface of theyarns.

11. A method comprising the steps of flatknitting a fabric from yarnscomprising cellulose acetate fibers carrying a conditioning agent, saidyarns being in normally dry condition, passing the fabric under tensionfrom the line of its formation to a take-up position, and internallyheating a narrow portion only thereof along each of the selvages duringsuch passage under tension by the application 01 a high frequencyelectric current to raise the temperature of the fibers inside the yarnsto a temperature which relieves internal fiber stresses and renders thefibers adhesive to bind the fibers in the interior of the yarns withoutserious deformation or loss of fiber identity in the fibers exposed onthe surface of the yarns.

EDGAR S. KENNEDY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,803,672 Lardy May 5, 19312,301,703 Humphreys Nov. 10, 1942 2,448,032 Kennedy Aug. 31, 19482,449,317 Pitman Sept. 14, 1948 2,460,566 Brown Feb. 1, 1949

